The present invention relates to high speed weaving machines and more particularly, to the heddle frames for use on high speed weaving machines.
In the past, heddle frames used in weaving machines were composed of a pair of end braces and a pair of laterally extending rails. The end braces were conventionally, rigidly attached to the top and bottom rails at each end. The end braces are free to slide in a guiding groove on a support on the weaving machine to form the shed during the weaving operation. With the advent of high speed weaving machines, which make as many sheds as 300 to 600 per minute, the reciprocating motion of the heddle frame was very rapid and the inertia of the heddle frame, owing to its weight, was very great. This caused frequent breaking of the heddle frames, particularly at the connection between the end braces and the top and bottom rails.
In an attempt to overcome such defects and to reduce the inertia of the heddle frame, the top and bottom rails have been made of light weight hollow aluminum beams. However, the aluminum rails are subjected to substantial bending which exerts a flexing movement of the connection between the end brace and the top and bottom rail. This flexing action results in fatigue of the metal comprising the end braces or the rails or both, thereby causing frequent failure of the heddle frame.
Several attempts have been made to overcome the problems created by the high speed weaving machines. One such attempt is shown in U.S. Pat. No. 4,022,252 issued May 10, 1977 to Hiroshi Ogura. In this patent, the end brace has a metal core, a portion of which is covered with plastic to provide additional strength. A pair of joining pieces project from the strengthened portion of the core of the end brace, as one body and form a tapered groove therebetween. These projections extend into the hollow body of the cross rails. The end brace is anchored to the cross rails by means of a wedged shaped member which is attached to the end brace by screws. The wedged shaped member enters the tapered groove, formed by the projecting pieces, so as to force the projecting pieces against the side walls of the cross rail, locking the end brace firmly to the cross rails. This joint is relatively rigid in that the projected pieces are firmly forced against the walls of the cross rail and provides little or no flexibility between the end brace and the cross rails. This arrangement makes for a stronger connection between the end brace and the cross rails but does not provide for the flexibility of the connection which is necessary to avoid unduly flexing or fatiguing the metal making up the end braces or the cross rails.
Another attempt to resolve the defects and deficiencies of the prior art heddle frames is shown in U.S. Pat. No. 4,230,159 issued Oct. 28, 1980 to Yoichi Shimizu. In this patent, the end brace is joined to the cross rail by means of a plastic projection which extends into the hollow space of a cross rail and is pinned to the cross rail by a single pin which permits the projection to pivot about the pin to provide for a flexible joint. A packing material 11 is packed between the space between the end brace and the cross rail to dampen the noise or pivoting action between the end brace and cross rail. This permits the flexibility of the joint but it is a design that cannot be readily disassembled for drawing in of the warps or for replacing component parts.